An underbite, medically termed Class III malocclusion, occurs when the lower jaw and its teeth position themselves forward of the upper jaw and teeth. This misalignment results in the lower front teeth biting in front of the upper front teeth. The direct answer to whether an underbite can return after treatment is yes, largely due to ongoing growth patterns and biological factors that constantly work to revert the jaw and teeth to their original positions.
Understanding Class III Malocclusion
Class III malocclusion is broadly categorized into two primary types: dental and skeletal. A dental underbite involves only the position of the teeth; the jaws are properly aligned, but the teeth are angled incorrectly. This type is generally easier to correct and stabilize because the underlying bone structure is harmonious.
The skeletal underbite involves a discrepancy in the size or position of the jaw bones, often characterized by mandibular prognathism or maxillary retrognathism. Skeletal discrepancies have a strong genetic component, often require comprehensive treatment, and carry a significantly higher risk of relapse. Functional underbites, or pseudo-Class III, occur when the jaw shifts forward due to an interference, but the underlying skeletal relationship is normal.
When the underlying cause is solely the bone structure, as in a true skeletal underbite, the forces of growth and genetics become powerful drivers of potential relapse.
Factors Driving Orthodontic Relapse
The primary reason an underbite tends to return is the continuation of growth in the lower jaw, which is difficult to predict or control. The mandible can continue its growth into the early 20s, especially in males, long after active orthodontic treatment has concluded. This late mandibular growth can effectively undo the previous correction by pushing the lower teeth and jaw forward again.
Biological forces, collectively known as soft tissue memory, also drive the teeth to return to their original positions. The periodontal ligaments and stretched gingival fibers act like elastic bands, attempting to pull the teeth back. The surrounding musculature, including the tongue, lips, and cheeks, exerts continuous pressure, and if the final tooth positions are not in harmony with these forces, relapse is likely.
If the initial correction did not fully address the underlying skeletal discrepancy, the risk of recurrence increases significantly. Attempting to correct a moderate to severe skeletal issue with only tooth movement—a process called dental camouflage—leaves the primary bone imbalance untouched. The forces of the uncorrected jaw structure constantly exert pressure on the teeth, pushing them toward relapse.
The Role of Retention in Stability
To counteract the strong biological tendency of the underbite to return, a strict and often indefinite retention phase is mandatory. Retention actively stabilizes the corrected position against the forces of growth and soft tissue memory, making it the most important factor for long-term success in Class III cases.
Retention protocols typically involve a combination of fixed and removable retainers. Fixed retainers are thin wires bonded directly to the back surfaces of the lower front teeth, offering continuous support against late crowding and forward movement. This stabilization is particularly beneficial in the lower jaw, which is prone to late growth changes.
Removable retainers, such as Hawley or clear Essix appliances, are often prescribed for the upper arch. These devices must be worn diligently, initially full-time and then transitioning to nighttime wear for many years, sometimes indefinitely. Patient compliance is the single most important factor to prevent relapse.
Long-term monitoring by the orthodontist is necessary, particularly for patients treated during their growth phase. Regular check-ups allow the practitioner to monitor for subtle signs of relapse or undesirable late growth. Addressing these small shifts early is far simpler than correcting a full relapse.